Automatic firearm.



K. KRNKA. AUTOMATIC FIREARM. APPLICATION FILED AUG 8 I913 Patented Jan.4,1916.

2 SHEETS-SHEET I.

'WIT/VEJSFJ' K. KRNKA. AUTOMATIC FIREARM. APPLICATION man AUG.8. 191s.

Patented Jan. 4, 1916.

2 SHEETS-SHET 2. N

WIT/v 35 61 7%? W y awyr m ATTY KARL KRNKA, OF HIRTENBERG,AUSTRIA-HUNGARY.

AUTOMATIC FIREARM.

Specification of Letters Patent.

' Patented Jan. 4., 1916.

Application filed August 8, 1913. Serial No. 783,691.

To all whom it may concern:

Be it known that I, KARL neer, a subject ofthe Emperor of Austriallungary, whose post-ofiice address is Hirtenbeizg, Empire ofAustria-Hungary, have invented certain new and useful Improvements inAutomatic Firearms, of which the following is a specification In LettersPatent 1,018,914 granted to me Feb. 27, 1912, I have described a breechmechanism for automatic fire arms in which the head of the rigidlylocked breech bolt is able to move a short distance to the rear and thecartridge case is able to move back for a limited short distance duringthe shot. For this purpose a small space is provided between the rigidlylocked breech bolt and the bolt head. When this space is equal to. forexample, 1.2 inn-"1.; then the cartridge, case, as also the bolt headmust both move back to a distance of 1.2 mm.. whereby the unlockingmember 0 is thrown back compulsorily only to a distance of 1.2 mm. Thefurther action is done solely by the energy of the motion. The greaterthe space between the breech bolt and the bolt head the greater will bethe momentum imparted to the unlocking member. This, however, increasesthe strain on the cartridge case.

This invention has for its object to avoid these drawbacks by providingthe necessary space for the rearward movement of the bolt head atanother point of the breech mechanism, thereby attaining an advantageousratio of transmission of motion, whereby the accompanying impact for theunlocking member is prolonged, although the cartridge case makes asimilar movement and is subjected to less strain. I

()no form of this invention is illustrated by way of example in theaccompanying drawings in which Figure lie the breach bolt with its head.Figs. 2 and 3 show a part of the developed casing in differentpositions. Fig. 4 shows the unlocking member with the rotary lugs. Fig.5 shows the breech bolt opened out, and Fig. 6 shows the breechmechanism. Figs. 7 to 9 show the firearm in longitudinal section. the.breech bolt being shown in its differcnt positions. Fig. 10 is asectional View taken on the line I-II of Fig. 7.

The breech bolt b with head a is formed in the usual manner, butwithouta space between the breech bolt and the bolt head.

IUKNKA, engi- The two right. hand bolt lugs 1, differ from the knownconstruction only by the feature that the impact surfaces 14 and 15 ofthe bolt lugs have different pitches or inclinations. For example, ifthe screw surface 14 has for Instance a pitch of 1 mm. for degrees; thesurface 15 has a pitch of 3 mm. for 60 degrees. The manner of lockingand unlocking is effected, however in the present case exactly as in thecase of the breech mechanism described in my aforesaid patent. Likewisethe manner of operation of the fire arm is the same.

The development of a part of the breech bolt sleeve 7: (Fig. 2) showsthe grooves 18 in which the bolt lugs move forward and also shows thelaterall deflected locking grooves. The bolt lugs 1n Fig. 3 are shown-1n completely locked position. As shown in Fig. 2, the impact surface 15fits home, but behind the impact surface 14 thereis left a space z of0.8 mm. Since the impact surface 15 has for 60 degrees such aconsiderable rise or pitch as 4 mm. it is not able to oifer a rigidresistance to the forceof the explosion, and therefore during the shotit slides into the position shown in Fig. 3. At thisinstant theintermediate space behind the surface14 disappears, so that-the lockingof the breech mechanism is rendered rigid, because the pitch of theimpact surface 14 has only 1 mm. for 60 degrees, and therefore the frontlug is able to offer a complete resistance. The bolt has thereforerotated together with its lugs through 16 degrees, and the breech boltsleeve bolt head and bolt have been moved hack 0.8 mm. t

The construction of the unlocking member 0 with its two pairs ofoppositely disposed and inclined lugs 2, and of the breech bolt with thehelical grooves or guideways 4, are clearly shown in Figs. 4 and 5 andcorrespond to the like parts exhibited in my U. S. a patent referred to.

The helical grooves 4 are made wider toward the rear end in order toprovide inan advantageous manner quite an appreciable amount of play orloose motion for the lugs 2. Fig. 3 shows the bolt after 'it has rotatedthrough 16 degrees, in consequence of the limited rearward movement of0.8 mm. When therefore the bolt 7) rotates through 16v degrees in thedirection of the arrow B (Fig. 5) the lugs 2 move into the positionshown in broken lines, because the unlocking member (Fig. 4), owing tothe arrangement of the bars 33 is not able to rotate with them, but iscompelled to slide back in the direction of the arrow A (Fig. 5). There- 0.8 mm., because the rotation B of 16 degrees has produced a slidingmovement of p the bolt Z; in the direction of the arrow C to the extentof 0.8 mm. The compulsory total sliding movement ofthe unlocking memberis therefore proved to be 12".g+0.8=3.5 mm.

whereas the breech bolt sleeve, the bolt head and the bolt were pushedback only to the extent of 0.8 mm. Consequently by this ratio oftransmitting the shock, the momentum of the unlocking member a is. morethan quadrupled. I The use of this effective ratio or transmission thusrenders an extremely small amount ofv rearward movement' of the end ofthe breech bolt sleeve sufficient. In the present casethere is nothmg toprevent the bolt 6 and the head a (Fig. 1) being made in one piece ifdesired.

1 The first position of the lugs 2 corresponds to the position shown inFig. 2, while the lugs'shown in broken lines in Fig. 5 cor respond tothe position shown in Fig. 3. At the moniient illustrated by Fig. 3, theprojectilehas left the muzzle of the fire arm, because so long as thesurface 14 o-f'the lockin lug is receiving the gas pressure, the un 100'ng member 0 cannot efiect a further ro-' tation of the bolt. For thesake of certainty, however, a small dead or loose motion of about '5 mm.is allowed to the four lugs by extending the unlocking grooves by 5 mm.in the rearward direction (Fig. 5). When therefore the unlocking membera has been thrown back through a distance of it must still move idlythrough a farther distance of 5 mm. before it commences to open thebreech by reason of its acquired kinetic'energy.

The opening and closing of the breech take place in exactly the samemanner as described in my aforesaid patent.

' Fig. 7 illustrates the completely locke breech, the bolt lugs 1 ofwhich together with theirimpact' surfaces 14 and 15 assume the positionwhich is shown in Fig. 2. The breech bolt sleeve k is rigidly screwed tothe barrel, thehead a, the breech bolt 6 and the unlocking member a arecompletely thrustforward so that the cartridge case is forced home intothe chamber.

The head a can not execute a rotary move ment in the breech bolt sleeveis being prevented from doing so purposely by the ejector-rod 35. Theinternal construction of the breech bolt 6 is disclosed in Fig. 5, Whilethe details of the unlocking member a are clearly shown in Fig. 4, beingmoreover also disclosed in the U. S. Patent 1,018,914. Fig. 9illustrates the completely unlocked breech and the guides (helicallyshaped grooves) of the unlocking member 0 are plainly visible. Thebolt-lugs 1 contained in these said guides have been indicated by dottedlines in Fig.5, so that the space a of the left hand lugs may be clearlyseen. In Fig. 2 the space 2 of the right hand lugs 1 is shown. I Thus itfollows that the bolt-lugs are shown in Fig. 7 in the same position inwhich they are indicated by dotted lines in Fig. 9. The

unlocking member 0 is likewise unable to execute a rotary movement as itcan only be led along in a straight line in consequence of the bars 3.The peculiar manner in which the bolt-lugs 1 arelodged in the guides onthe breech bolt being completely locked is not only illustrated by Figs.,2 and 9, but also in Fig. 10. When the cartridge is discharged themembers a, b and 0 of the breech move into the position shown by Fig.'8. The

corresponding position of'the bolt-lugs 1 is shown in Fig. 3. The breechbolt has ro tated through 16 in consequence of the pressure exerted bythe rear end of the cartridge, this by reason of the co-action betweenthe lugs 2 and guideways '4, as indicated'in Fig.

5, and as a result of which the impact surface 14 has been brought up toan absolute close contact, the said space 2 having disappeared. By thismeans the breech-bolt b together With the head a have been moved back0.8 mm. as is shown by Figs. 3 and 8. Simultaneously with the above, theunlocking member 0 in Fig. 8 has been thrown 11 rearward 2.7 mm. out ofthe breech-bolt b as the said unlocking member maintains a relation tothe breech-bolt 6 similar to that of a screw to its nut, as is disclosedin- Figs. 4 and 5. If now the position assumed bythe unlocking member ain Fig. 7 is compared withthat assumed in Fig. 8 it will be seen thatthe said unlocking member has been thrown back compulsorily all in allby 3.5 mm. L

while the breech bolt on the other hand has only been forced hack 0.8mm., maintaining this position (Fig. 8) immovably for the provided witha back-lash, as indicated in Fig. 5. Now while the unlocking member 0(as per Fig. 8) pursues the distance m the projectile has already leftthe muzzle of the fire arm. It thus follows that the unlockingpiece 0has obtained a great deal of kinetic energy, and by the force ofmomentum continues beyond the distance as while at the same time. and inconsequence of its rearward movement beyond r0, causing the breech-boltto rotate in such a manner that the noses of the bolt-lugs 1 (Fig. 9)fit onto the screw surfaces 19 (Fig. 9). The pitch of these said screwsurfaces is however so great that the breech-bolt b is not held up inits movement thereby entering ,along with its bolt-lugs 1 into thelongitudinal grooves 18 and being obliged to completely slide back as isshown by Fig. 9. This Fig. 9 moreover discloses that the unlockingmember 0 has still farther moved out of the breech-bolt b in the courseof the movement above described and in the position now assumed themembers a, Z) and 0 together with their auxiliary parts slide back as aresult of which a closing or accumulator spring a f is compressed in themanner already known in connection with automatic firearms, By thesubsequent expansion of the said spring the bolt-lugs 1 of thebreech-bolt b (Fig. 9) reassume the position indicated by broken linesin Fig. 9 as a result of which the position disclosed by Fig. 7 is againobtained.

An advantageous simplification of the breech mechanism is produced whenthe spring 6 f constitutes the closing spring and also the firingspring, the firing pin d being able to move freely to and fro in thehead a and in the unlocking member 0 without be-. ing able to carry theunlocking member with it, for instance owing to a repulsion (on strikingthe percussion cap) Consequently in the closing of the breech all theparts a b c and cl will be moved forward compulsorily by the force ofthe spring .6 f until the nose 17 of the firing pin 01 is caught by thetrigger sear s as shown in Fig. 6. From this instant the parts a b and'care caused to move by reason of their acquired momentum into theirclosing positions as shown in Fig. 6.

After the trigger is pulled, the firing pin d v joins the other partscompulsorily. As a consequence of this simplification the lugs 16 andannular groove 17 in the breech bolt sleeve described in my aforesaidpatent may be dispensed with.

The breech bolt 6 is designed to be actuated to impart initial unlockingmovement to the breech bolt sleeve is synchronously with the firing ofthe cartridge. and to this end the head a is provided. The head ismounted within the forward end of the breech bolt sleeve and is designedto have a relatively short axial movement independently of the breechbolt sleeve, the extent of this movement being indicated by thecharacter a. The head is secured against axial displacement in thebreech bolt sleeve through the medium of the ejector rod 35, as clearlyshown in Figs. 7, 8 and 9.

The means for closing and locking the breech bolt sleeve following itsrecoil under.

gas pressure consists of the accumulator spring 6 7' which, at one endis coiled about a stud j projecting rearward from the firing pin head (5the other end of the spring being disposed to bear against the rear wallof the breech casing C, which casing is in all essential respects acounterpart of that shown in my U. S. patent to which refer ence hasbeen made.

As outlined at the beginning of the specification, the salient object ofthe invention is to shift the recoil space for the bolt head from itsfront to another point, in this instance to its rear, and this isaccomplished, first by having the bolt head rigid with the bolt, andsecondly by the provision of the novel arrangement of the lugs 1 and 2,and the guideways 4, together with the other elements coactingtherewith, notably the accumulator spring, the arrangement and operationof which eliminates the necessity of the employment of the spring 23shown and described in my U. S. patent, thereby materially simplifyingthe construction of the breech mechanism, thus measurably increasing itswear resisting qualities and minimizing its liabiltiy to breakage.

Having now particularly described and ascertained the nature of my saidinvention and in what manner the same is to be performed, I declare thatwhat I claim is 1. In firearms, in combination, a breech casing providedwith longitudinally extending grooves having laterally extending lockinggrooves communicating therewith, and a breech bolt rotatable within saidcasing and provided with front and rear lugs adapted to engage saidlocking grooves, said lugs having impact surfaces co-acting with therear walls of said locking grooves when the firearm is discharged,saidimpact surfaces difl ering from one another in pitch or inclination.

2. In firearms, in combination, a breech casing provided withlongitudinally extending grooves having laterally extending lookinggrooves communicating therewith, and a breech bolt rotatable within saidcasing and provided with front and rear lugs adapted to engage saidlocking grooves, said lugs having impact surfaces co-acting with therear walls of said locking grooves when the firearm is discharged, thepitch or inclination of the impact surface of the rear lug being greaterthan the pitch or inclination of the impact surface of the front lug.

3. In firearms, in combination, a breech casing provided withlongitudinally extending grooves having laterally extending lockinggrooves communicating therewith, and a breech bolt rotatable Within saidcasing and provided with front and rear lugs adapted to engage saidlocking grooves, said lugs having impact surfaces co-acting with therear Walls of said locking grooves When the firearm is discharged therebeing a space between the impact surface of the front lug and the rearwall of its corresponding lock- 10 ing groove When the breech block isin firing position, said impact surfaces differing from one another inpitch or inclination.

In testimony whereof I have signed my name to the foregoingspecification in the presence of two subscribing witnesses.

KARL KRNKA.

\Vitnesses GUSTAV \VoLFF, AUGUST FUGGER.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents.

Washington, I). G.

